embryo transfer

Several recent studies have shown the beneficial effect of platelet-rich plasma (PRP) in improving endometrial function in cases with repeated implantation failure and thin endometrium. However, the mechanism of this effect is unclear.

To investigate the direct effect of PRP on the implantation process during embryo transfer (ET) in cases without an obvious history of abnormality on implantation.

In this randomized clinical trial study, 55 infertile women (20-40 yr) who were candidates for intracytoplasmic sperm injection referred to the Infertility Center of Fatemiyeh hospital in Hamadan, Iran between September 2022 and 2023were randomly divided into intervention and control groups. In the intervention group, PRP was added to the ET medium, while in the control group, a routine ET medium was used. After ET, chemical and clinical pregnancy were measured.

In the intervention and control groups beta human chorionic gonadotropin positivity 14 days after transfer was 33.3% and 39.3%, consecutively (p = 0.646). At 21 day post-transfer, gestational sac was observed in 33.3% and 35.7% of cases (p = 0.646). By 28 days after transfer fetal heart activity was detected in 33.3% and 35.7% of cases (p = 0.631).

The addition of autologous PRP at the time of ET does not have a direct positive effect on embryo implantation, and the observation of positive effects in previous studies may be indirectly on the uterine microenvironment, which requires time.

Recurrent implantation failure (RIF) refers to the inability to achieve pregnancy after two or three high-quality embryo transfers, representing a significant challenge in in vitro fertilization (IVF). In these women, endometrial perfusion is diminished, and uterine artery resistance is increased. The purpose of this study was to investigate the effect of oral L-arginine on uterine artery resistance and the results of IVF in infertile women with RIF.

This clinical trial was conducted on 72 infertile women, candidates for frozen embryo transfer, with a history of two previous transfer failures, who were referred to Fatemieh Infertility Center. Patients were randomly divided into two groups of control and intervention. In addition to standard drug treatment and protocol, the intervention group received oral L-arginine supplementation (3 gr daily for 20 days), beginning from the luteal phase. Uterine artery resistance index (RI) and pulsatility index (PI) were measured using two-dimensional Doppler ultrasound. Statistical analysis was performed using SPSS software, version 26, with a significance level set at less than 5%.

Statistical analysis revealed a significant difference in the right uterine artery RI (p=0.002), left uterine artery RI (p=0.019), clinical pregnancy rate (p=0.003), and chemical pregnancy rate (p=0.006) between the two groups.

This study demonstrates that the daily administration of 3 grams of oral L-arginine for 20 days in women with RIF effectively reduces uterine resistance and increases both clinical and biochemical pregnancy rates.

Fresh embryo transfer has been decreasing because of advancements in vitrification techniques and safety concerns related to ovarian hyperresponse. However, in normal responders, clinical outcomes appear to be comparable with those with frozen embryo transfer. This study aimed to determine factors that influence successful fresh embryo transfer.

This retrospective cohort study included 521 women who underwent in vitro fertilization (IVF) and fresh embryo transfer at King Chulalongkorn Memorial Hospital, Thailand. Patients’ clinical data, embryo details, endometrial characteristics (thickness and pattern), and embryo transfer procedures (tip and flow during transfer, embryo placement location, difficulty of the procedure, and presence of blood and mucous at catheter) were analyzed. Chi-square test, Fisher’s exact test, Student’s t-test, and logistic regression were performed for data analysis. A p-value of <0.05 was considered statistically significant.

The overall clinical pregnancy rate was 17.1%. Women aged >40 years were less likely to have a clinical pregnancy than those aged <35 years (adjusted odds ratio [aOR] 0.422; 95% confidence intervals [CI] 0.196-0.908, p=0.027). Day 3 embryo transfer showed a significant decrease in clinical pregnancy compared with blastocyst transfer (aOR 0.514; 95%CI 0.287-0.923, p=0.026). In the subgroup analysis for blastocyst transfer, women with good-quality blastocyst (≥322) were 2.439 times more likely to have a clinical pregnancy than those with poor-quality blastocysts (aOR 2.439; 95%CI 1.199-4.962, p=0.014).

Advanced age and day 3 embryo transfer were significantly associated with low clinical pregnancy rates in fresh embryo transfer.

Endometrial compaction (EC) is an ultrasound evaluation method that may predict assisted reproductive technology outcomes.

This study aimed to assess the impact of EC on assisted reproductive technology outcomes in frozen embryo transfer cycles with hormone replacement therapy.

In this cross-sectional study, 100 women who underwent first or second frozen embryo transfer cycle at Yazd Reproductive Sciences Institute, Yazd, Iran from June to October 2024 were included. Endometrial thickness was compared between the day of starting progesterone and embryo transfer day. Then participants were divided into 2 groups, no compaction and compaction group. Biochemical, clinical, and ongoing pregnancy rates (OPR) were assessed between the 2 groups.

Statistically significant differences were observed in biochemical, clinical, and OPR between the compaction and no compaction groups. Logistic regression analysis demonstrated significantly higher pregnancy rates in EC 10-15% and > 15%. We found a significant influence of EC 10-15% (p = 0.02, p = 0.01, p = 0.01), and EC > 15% (p = 0.002, p = 0.001, and p = 0.002) on biochemical, clinical, and OPR, respectively.

EC after progesterone administration in hormone replacement therapy-frozen embryo transfer cycles can increase biochemical, clinical, and OPR. The percentage of EC changes also influence the outcomes of these cycles.

Hormone replacement therapy (HRT) is the preferred protocol for endometrial preparation. Progesterone is important for successful implantation and the outcome of assisted reproductive techniques (ART). The impact of serum progesterone concentration on pregnancy outcomes has been extensively studied; however, there are conflicting results for dosage and route of administration. This study investigates the association between serum progesterone levels on embryo transfer day and assisted reproductive technique outcomes in frozen-thawed embryo transfer (FET).

This prospective cohort study was conducted on women who underwent FET. Participants received HRT with 6 mg of oestradiol valerate and 400 mg of micronized vaginal progesterone, along with 50 mg of intramuscular (IM) progesterone for endometrial preparation. Serum progesterone was assessed before embryo transfer. The primary outcome was live birth rate (LBR).

Overall, 190 infertile women underwent cleavage FET and were categorised according to the presence (group I: n=38) or absence (group II: n=152) of live birth. Group I women had significantly higher progesterone levels on the transfer day (34.48 ± 8.95 ng/ml) compared to group II women (29.83 ± 11.076 ng/ml, P=0.008). We divided the serum progesterone values into quartiles and observed significantly lower clinical pregnancy rates in the Q1 quartile (progesterone ≤23.84 ng/ml). Receiver operating characteristic (ROC) curve analysis indicated a significant threshold for progesterone level on the day of embryo transfer in terms of LBR, with an area under the curve (AUC) of 0.64 [95% confidence interval (CI): 0.54-0.73, P<0.001]. The estimated threshold was 26.95 ng/ml, with a sensitivity of 82% and a specificity of 43%.

The present study showed a significant positive association between serum progesterone levels on transfer day and LBR in FET cycles after patients received a combination of vaginal and IM progesterone supplements. Monitoring of serum progesterone in FET cycles are recommended. 

Endometrioma, a common manifestation of endometriosis, often indicates the severity of the disease. In vitro fertilization and embryo transfer (ET) are key therapeutic strategies for infertility associated with endometriosis. However, the optimal type of ET (frozen or fresh) and its impact on pregnancy success rates remain debated, with limited studies available.

This historical cohort study aimed to compare fertility and neonatal outcomes, focusing on live birth rate (LBR), clinical pregnancy, and implantation rates in women with endometrioma-associated infertility, between fresh and frozen embryo transfer (FET).

In this historical cohort study, the medical records (files) of 289 women diagnosed with endometrioma-related infertility, who underwent in vitro fertilization/intracytoplasmic sperm injection treatment at Royan Institute, Tehran, Iran between March 2016-2021 were reviewed. Ultimately, 200 files that met the established criteria were selected for review. The extracted data was then compared between groups: FET (n = 121) and fresh ET (n = 79).

No significant differences were observed between the groups in terms of demographic characteristics and endometrioma size. The only significant difference in fertility outcomes was the LBR, which was 36.4% for the FET group compared to 22.8% for the fresh ET group (p = 0.04). No significant differences were observed in neonatal outcomes between the groups. Overall, our study suggests that FET may lead to higher LBRs in women diagnosed with endometrioma.

Our study suggests that FET may lead to higher LBRs in women diagnosed with endometrioma.

Superovulation is a crucial component of assisted reproductive technology. Inducing superovulation with Gonadotropin-releasing hormone (GnRH) can lead to ovarian hyperstimulation, potentially affecting reproductive outcomes.

This study aimed to examine the effects of GnRH treatment on superovulation response and embryo recovery in Holstein heifers.

Twenty-one Holstein heifers (age: 135.15 months; weight: 361.05 kg) were selected based on their general health status and ovarian function. All heifers received two consecutive doses of prostaglandin F2α and underwent superovulation. The heifers were inseminated twice: Once at the onset of standing estrus and again 12 hours later. In the treatment group (13 heifers), a single dose of GnRH was administered simultaneously with the second insemination. The superovulation response was evaluated based on the number of corpus luteum (CL), unovulated follicles (UoF), total recovered embryos/ova, and the number of transferable embryos, using logistic regression with the GENMOD procedure in SAS.

The mean number of CL was not significantly greater in the control group (13.6) compared to the GnRH group (11.4). The average number of UoF was similar between the two groups (P = 0.1853). However, the control group had a significantly higher average total number of recovered embryos/ova (7.7) compared to the GnRH group (2.1). Additionally, the control group progesterone more transferable embryos, with an average of 2.5, while the GnRH group averaged 0.7 (P < 0.0062).

Gonadotropin-releasing hormone likely deactivated the oviduct by disrupting the balance of estradiol and estrogen, leading to a reduction in both the total number of embryos and the number of transferable embryos in heifers.

Patients with thin endometrium undergoing frozen-thawed embryo transfer often encounter challenges with pregnancy outcomes. Enhancing endometrial receptivity and immune tolerance may improve these outcomes. To investigate the effects of intrauterine perfusion of granulocyte colony-stimulating factor (G-CSF) and human chorionic gonadotropin (HCG) on regulatory T cells (Tregs) and pregnancy outcomes in patients with thin endometrium undergoing frozen-thawed embryo transfer. 150 patients with thin endometrium were randomly assigned to three groups: a control group that received no intervention, an HCG group, and a G-CSF group. The effectiveness of the treatments was assessed by comparing uterine parameters, Treg levels, and pregnancy outcomes across the groups. The HCG and G-CSF groups exhibited significant improvements compared to the control group, including increased endometrial thickness, enhanced blood flow, higher expression of endometrial receptivity markers (integrin αvβ3, osteopontin), and elevated Treg levels. Notably, the G-CSF group demonstrated even greater enhancements compared to the HCG group, with significantly higher endometrial thickness, better blood flow, increased receptivity markers, and elevated Treg levels. Additionally, the G-CSF group achieved significantly higher biochemical and clinical pregnancy rates compared to both the HCG and control groups. This highlights the potential of G-CSF in improving pregnancy outcomes for patients with a thin endometrium. The intrauterine perfusion of G-CSF significantly enhanced pregnancy outcomes in patients with thin endometrium by improving endometrial blood flow, immune tolerance, thickness, Treg induction, and embryo implantation. These findings suggest that G-CSF could be a promising therapeutic option for this patient population.

Currently, frozen embryo transfers (FET) account for 41% of all embryo transfer cycles. Vaginal progesterone preparations have become the leading choice for luteal phase support due to their convenient application; however, using only vaginal progesterone during FET cycles results in a lower ongoing pregnancy rate.

This study aimed to investigate whether replacing intramuscular (IM) progesterone with oral dydrogesterone in FET cycles affects pregnancy outcomes or not.

In this cross-sectional study, pregnancy outcomes were analyzed in women who underwent cleavage stage FET during an endometrial preparation cycle using hormone replacement therapy at Yazd Reproductive Sciences Institute, Yazd, Iran, between April 2023 and November 2023. The study examined 2 groups based on a luteal phase support regimen: the dydrogesterone group, which received vaginal progesterone and oral dydrogesterone, and the IM progesterone group, which received vaginal progesterone and IM progesterone. Data were extracted from patient files to compare outcomes between the 2 groups.

A total of 960 cycles meeting the inclusion criteria were analyzed, with 292 women in the dydrogesterone group and 668 women in the IM progesterone group, and pregnancy outcomes were compared between the 2 groups. The chemical pregnancy rates (28.4% vs. 29.9%, p = 0.636), clinical pregnancy rates (25.3% vs. 26.9%, p = 0.604), and ongoing pregnancy rates (21.9% vs. 23.8%, p = 0.525) were lower and miscarriage rates (14.7% vs. 11.7%, p = 0.210) were higher in dydrogesterone group compared to IM progesterone group, although this difference was not statistically significant.

Based on the ease of use and similar pregnancy outcomes of oral dydrogesterone, it can potentially replace the daily injections of IM progesterone.

Frozen embryo transfer (FET) has been increasingly used due to advancements in cryopreservation techniquesand the safety advantages. This study aims to determine various factors influencing the successful FET. Retrospective cohort analysis included 1112 women who underwent programmed FET betweenJanuary 2012 and October 2022, at King Chulalongkorn Memorial Hospital, Thailand. Patient characteristics, embryocharacteristics, endometrial preparation protocol, endometrial characteristics (thickness, pattern), embryo transferprocedure (tip and flow during transfer, embryo placement location, the difficulty of the procedure, presence of bloodand mucous at catheter), and operator factor were analyzed. Multiple logistic regression analysis was used to assess therelationship between collected variables and successful embryo transfer which is defined by clinical pregnancy. The overall clinical pregnancy rate was 34.2%. Women aged 35-40 years and >40 years were less likelyto have a clinical pregnancy compared to those aged <35 years [adjusted odds ratio (aOR): 0.523; 95% confidenceintervals (CI): 0.360-0.757, P<0.001 and aOR: 0.260; 95% CI: 0.152-0.434, P<0.001, respectively]. Obese womenwith body mass index (BMI) ≥25 kg/m2 were significantly associated with decreased clinical pregnancy (aOR: 0.632;95% CI: 0.403-0.978, P=0.042) compared to those with normal BMI. Day-3 and day-4 embryo transfer showed a significantdecrease in clinical pregnancy compared to blastocyst transfer (aOR: 0.294; 95% CI: 0.173-0.485, P<0.001and aOR: 0.497; 95% CI: 0.265-0.900, P=0.024). Double embryo transfer (DET) was 1.78 times more likely to have aclinical pregnancy than women with single embryo transfer (SET) (aOR: 1.779; 95% CI: 1.293-2.458, P<0.001). Thecycles with endometrial thickness <8 mm were associated with a decrease in clinical pregnancy compared with thosewith a thickness ≥8 mm (aOR: 0.443; 95% CI: 0.225-0.823, P=0.013). Older age, obesity, non-blastocyst transfer, single embryo transfer, and endometrial thickness of <8 mmwere significantly associated with a decreased clinical pregnancy in programmed FET.

Assisted reproductive technology (ART), offers hope for many infertile couples by increasing the chance of successful pregnancy. The success of in vitro fertilization depends on various factors, in which embryo transfer (ET) is one of the critical steps influencing in vitro fertilization success rates. Extended embryo culture and blastocyst-stage ET have been considered in ART due to their potential benefits including improved implantation rates.

This study aimed to compare the outcomes of sequential ET vs single cleavage-stage ET in women undergoing a fresh ET cycle with a limited number of embryos.

This randomized clinical trial was conducted on 140 women undergoing infertility treatments and candidates for fresh ET at the Research and Clinical Center for Infertility, Yazd, Iran from August 2023 to January 2024. Women with a number of embryos from 2-5 (≥ 2 and ≤ 5 available embryos) were randomly divided into 2 groups: One group underwent sequential ET (one cleavage-stage ET followed by one blastocyst ET) and the other group underwent single-step 2 cleavage-stage ET. The primary outcome was clinical pregnancy, and the secondary outcome included chemical pregnancy and early abortion rates.

Our findings showed significantly higher rates of clinical (33.5% vs 13.6%, p = 0.003) and chemical (41.3% vs 18.2%, p = 0.004) pregnancies in the sequential ET group compared to the single-step cleavage ET group. The early abortion rate was higher in single-step cleavage ET (13% vs 44.4%, p = 0.053).

Sequential fresh ET is a useful choice in women who have a limited number of embryos and can improve ART outcomes.

To evaluate the associations between serum and follicular zinc levels and the response to intracytoplasmic sperm injection (ICSI). Patients and

A prospective cohort study was conducted between May 2022 and May 2023 on 120 infertile women randomly selected based on specific criteria. The patients were classified into three groups according to stimulation response. Serum zinc level was measured in all patients on the day of ovarian stimulation, and follicular fluid zinc level was measured at the time of pickup. We monitored the patients to evaluate the correlation between serum and follicular zinc levels, as well as the reaction to ovarian stimulation. We assessed oocyte quality and quantity, fertilization rate, embryo quality, and clinical pregnancy rate.

The participants were homogenized at comparable ages. The 120 patients were classified into three groups according to the number of oocytes retrieved after ovum pick-up: four oocytes were categorized as poor responders (n = 40), 4-15 retrieved oocytes were categorized as normal responders (n = 40), and >15 retrieved oocytes were categorized as hyper-responders (n = 40). The poor responders had significantly lower serum and follicular zinc levels than the others. There was a significant difference between the three groups (P value = 0.0001). There was a direct positive correlation between serum and follicular zinc levels. However, there was a moderately negative correlation between the serum and follicular zinc levels and the total gonadotropin dose. On the other hand, there was a slightly positive link between the amount of zinc in the serum and follicles and the response to stimulation in the ICSI cycle in terms of the number of oocytes, ovarian sensitivity index (OSI), follicular output rate (FORT), and follicle-to-oocyte index (FOI). There was a strong positive correlation between serum and follicular zinc levels and the fertilization rate and number of MII but a weak positive correlation with the number of MI. All significant correlations between serum and follicular zinc levels were found to be predictors of clinical pregnancy.

The serum zinc level at stimulation day was reflected in the follicular fluid zinc levels after stimulation and at the time of ovum pick-up. Both of them predict the success of an ICSI cycle, including the response to stimulation and the pregnancy rate. The serum zinc level can also indicate cases that may progress to clinical pregnancy. It is crucial to measure the blood zinc levels of women preparing to undergo ICSI. The start of ICSI program should be delayed until the serum zinc level is optimal, as it is a predictor of the response to stimulation and the outcome of the ICSI cycle. Encouraging adequate zinc intake prevents the potential impact of altered zinc levels on the success rate of these women’s responses to stimulation.

 Islamic Republic of Iran has provided a legal framework for embryo transfer so that fertility becomes possible with third party intervention. The use of this method of fertility as well as its effects and rules are subject to cultural, social and religious factors. The brief nature of the embryo donation law indicates the lack of adequate measures for the child’s future. The present study aimed to review the embryo donation law in Iran and some challenges in determining the rights of the child. This study employed a library, descriptive and analytical method and is based on Shia jurisprudence and law books. By using the keywords of “Donation, Alimony, Custody, and Inheritance”, various aspects of the embryo donation law have been investigated. Article 3 of the Embryo Donation Law considers the duties and responsibilities of the couples who donate the embryo and the born child in terms of maintenance, alimony and being mahram (. An unmarriageable kin in Islamic Sharia legal terminology), similar to the duties and responsibilities of children and parents. However, the important issues of lineage and inheritance are not considered. Neither it elaborates compliance with the principle of confidentiality and the non-identification of the genetic parents, the coercive guardianship of the father, and the prohibition of marriage (being mahram). There is neither enough clarity about the method of evaluating the recipient couple’s moral competence, the limit of the number of gamete donations, alimony, or custody. It is necessary to explain the kinship and genetic inheritance, amend birth certificate registration law, specify the rejection of anonymity to prevent the phenomenon of mixing lineage based on Shia jurisprudence, or to add new materials to this law.

COVID-19 can have potential pathogenic effects on the oocyte and embryos, but there is limited data about its impact. This study aimed to investigate the COVID-19 impact on the outcome of Assisted Reproduction Techniques (ART) methods.

This case-control study was conducted on 190 infertile women who underwent oocyte retrieval at Yas Hospital in vitro fertilization (IVF) department affiliated to Tehran University of Medical Sciences, from October 2021 to October 2022. The case group was defined as women whose PCR test was positive on puncture day and the control group was women with COVID-19 negative tests on puncture day. The study outcome measurements included the number of oocytes retrieved and the number and quality of embryos. Finally, the data were analyzed by SPSS 24.

The mean age of the participants was 32.89 ± 5.58 years with an age range of 18-49 years. No significant difference was observed between the two groups regarding baseline variables.  The mean number of oocytes was significantly (p =0.001) lower in the case (6.68±4.25) group versus the control (9.07±4.10) group. While there was no statistically significant difference regarding the mean number of embryos in the study groups, No grade A embryos were observed in more than half (57.5%) of the women in the case group. Furthermore, the frequency of grade C embryos on average was 1.08±1.11 in the case group and 0.57±0.75 in the control group, with a statistically significant difference (p =0.010).

The findings of this research highlighted that women infected with COVID-19 on the puncture day have a lower number of oocytes and also good-quality embryos.

Since the advent of assisted reproductive technology, different variables have been shown to affect pregnancy outcomes. One of the most prevalent studied events is the premature rise in serum progesterone concentrations on the day of trigger administration during cycles of ovarian stimulation. This phenomenon, classically known as premature luteinization, has been observed significantly for decades and has been linked to adverse pregnancy outcomes and lower live birth rates. Ultimately, a quest to find a precise serum progesterone concentration cut-off value that can be effectively used to predict pregnancy outcomes prior to trigger administration is still underway. The purpose of the current research was to study the available literature on the relationship between serum progesterone on the day of trigger administration in controlled ovarian stimulation cycles used for IVF in an attempt to identify a cut-off serum progesterone concentration that can be used to effectively predict future pregnancy outcomes in fresh transfers. This study is a review of the literature and is based on information and data gathered from 36 published articles. The majority of the literature shows that a serum progesterone concentration cut-off of 1.5 ng/ml (4.77 nmol/L) can be used prior to trigger administration to effectively predict pregnancy outcomes. Premature progesterone elevation on the day or prior to the trigger administration is associated with adverse pregnancy outcomes in IVF cycles. Other factors such as follicle number, serum concentration of other hormones, and ovarian response to ovarian stimulation should also be considered to predict the success of IVF protocols.

Trans-abdominal ultrasound (TAUS) and transvaginal ultrasound (TVUS) are used for embryo transfer. However, few studies were conducted to compare the methods and assess their effect on pregnancy outcomes.

A retrospective cohort study was conducted at Mahdieh Hospital in Tehran, analyzing 506 ICSI cycles with fresh embryo transfer. The study period was from April 2019 to March 2022. Following the evaluation of patients’ profile, they were divided into two groups of TAUS (n=250) and TVUS (n=256). The pregnancy outcomes included positive test of β-HCG, history of miscarriage, ectopic pregnancy (EP), clinical pregnancy, and the duration of the embryo transfer were compared between two groups. Mann-Whitney U test, Pearson Chi-Square test, Fisher's exact test, and logistic regression were used for data analysis.

The rate of chemical and clinical pregnancy in the TAUS group was higher compared to the TVUS group, which was statistically significant (p<0.05). The rate of live term birth and live preterm birth was higher in the TAUS group compared to the TVUS group, though the difference was insignificant. Moreover, EP and abortion rates were higher in TVUS group compared to the TAUS group, but the differences were not statistically significant. The odds ratio of achieving pregnancy was higher with TAUS compared to TVUS, but this was only statistically significant for the age variable.

The use of TAUS method appears to be associated with improved pregnancy outcome, including higher rates of chemical and clinical pregnancy, compared to TVUS. Yet, further research is needed to confirm these findings and elucidate underlying mechanisms.

There is a definite shift in assisted reproductive centres from cleavage-stage embryo transfer (ET) toblastocyst transfer that is attributed to improvements in laboratory environments and advances in the development ofembryo culture media. The aim of the study was to investigate the reproductive outcomes of thawed cleavage-stage ET versusblastocysts derived from an extended culture of these embryos. This open-label, randomised, parallel group clinical trial study enrolled 182 women aged ≤37years who underwent frozen-thawed ET from November 2015 to June 2020 at Royan Institute Research Centre, Tehran,Iran. The women were randomly assigned to either the thawed cleavage ET group (n=110) or the post-thaw extended cultureblastocysts group (n=72). The primary outcome measure was the clinical pregnancy rate. Secondary outcome measureswere implantation rate, live birth rate (LBR), and miscarriage rate. A P<0.05 indicated statistical significance. There were no significant differences between the two groups in terms of demographic characteristics. Boththe mean numbers of embryos transferred and good quality embryos transferred were significantly lower in the post-thawextended culture blastocysts group compared to thawed cleavage-stage ET cycles. However, the post-thaw extendedculture blastocysts group had higher clinical pregnancy (56.94 vs. 40.91%, P=0.034), implantation (34.43 vs.19.84%, P=0.001) and live birth (49.3 vs. 33.63%, P=0.036) rates compared to the thawed cleavage-stage ET group.Miscarriage and multiple gestations rates were comparable between the groups. These results allow us to take a position in favour of post-thaw extended culture blastocysts; thus, it isimportant to improve the post-thawing extended culture technique (registration number: NCT02681029).

Based on the laboratory assays, there is no definitive decision about embryo selection with the proper embryogenic stage for successful transfer in the in-vitro fertilization (IVF) technique leading to live birth.

This experimental study critically aimed to evaluate the efficacy of embryo transfer in cleavage and blastocyst stages based on the Identical Population (IP) concept.

The IP concept was explained based on several critical points, including the strain (Balb/c), weight (30 g), age (six and eight weeks for females and males, respectively), number of previous sexual cycles, and the same generation. All embryos in each group were divided into grades A, B, and C. Finally, the produced embryos were transferred by trans-cervical procedure, and the mortality rate was recorded.

The number of implantation sites and live births increased in all grades of the blastocyst stage compared to the cleavage stage. The number and percentage of implantation sites in blastocysts and cleavage stages were 11 (45.83%) vs. 3 (8.57%) for grade A, 8 (29.62%) vs. 1 (5.26%) for grade B, 2 (10%) vs. 0 (0%) for grade C (P > 0.05), and number and percentage of live births in blastocysts and cleavage stages were 5 (20.83%) vs. 1 (2.85%) grade A, 3 (11.11%) vs. 0 (0%) grade B, and 1 (5%) vs. 0 (0%) grade C (P > 0.05).

Based on the results, the frequency of implantation sites and the live birth was higher in blastocyst transfer than in the cleavage stage in IVF.

 In vitro fertilization has advanced in many ways, and new techniques are challenging. Blastocyst transfer is an alternative method for embryo transfer (ET) to improve in vitro fertilization outcomes.

 The present study was performed to determine the effect of pregnancies resulting from ET in the blastocyst stage compared to the cleavage stage in frozen cycles to select a better method of assisted reproduction.

 This cross-sectional study was conducted on 194 women who referred to the Yazd Reproductive Sciences Institute, Yazd, Iran, between April 2019 and December 2020. They had a frozen ET as either cleavage or blastocyst (n = 97/each group). The study compared the pregnancy and fetal outcomes in the 2 groups of ET at the cleavage and blastocyst stages.

 The results showed that the blastocyst stage group had higher levels of anti-Mullerian hormone, ovule number, 2 pronuclear number, and embryo number than the cleavage stage group. The frequency of chemical pregnancies was 52.6% and 36.1% in blastocyst and cleavage group respectively (p = 0.02). Also, the frequency of clinical pregnancies was 41.2% and 22.7% in blastocyst and cleavage group respectively (p < 0.001). No statistically significant difference was observed between 2 groups in abortion, preterm delivery, multiple births, preterm premature rupture of membranes, gestational diabetes and preeclampsia, ectopic pregnancy, neonatal hospitalization in Neonatal Intensive Care Unit, and fetal abnormalities (p > 0.05).

 The results showed that transmission in the blastocyst stage compared to the cleavage stage is associated with an increase in chemical and clinical pregnancy, while other pregnancy outcomes are the same in both groups.